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Actually the C2D runs slightly cooler than CD. There was a thermal test done by macworld I think where the new Macbooks ran about 5 degrees cooler than the original Macbooks. Also I read that the C2D are more effecient with power consumption. So the batter life may be a little more.

basically cd is a 32 bit and the C2D is 64 bit. C2D is better but runs hotter but not by much. Also they can take more ram. I maybe wrong a newbie too, please correct me if i am wrong!

C2D also have a quicker clock speed, but that d&#165;goes without saying.

The improvements architecturally that Core2Duo brings are more L2 cache (4mb vs 2mb) and there are more pipelines and decode stages within the CPU, making it more efficient and the addition of EM64T technology (which has been in AMDs Athlon 64 series for 4 years).

In terms of clock speeds, in notebooks, Core Duo ranges from 1.2ghz to 2.33ghz. C2D ranges from 1.06ghz to 2.4ghz. Most people will end up with the same speed processor (2ghz is typical), but clock for clock, the C2D can do more work.

Here is the real kicker. The C2D is designed to run on an FSB of anything from 533mhz to 800mhz. 800mhz is the optimum speed. The CD only runs on 667mhz. However, all Macs only have C2D's running on 667mhz as well as their CD's, meaning they're essentially crippled.

Finally, the RAM each chip can address is the same. The C2D is a better CPU, but to get the most out of it, you need the 800mhz FSB, which I expect Apple will introduce next year.

In the land of the blind, the one-eyed man is stoned to death.
- Joan D. Vinge

Both CPUs are 32-bit - this is the 2nd time I have seen someone here say C2D is 64-bit, but that is wrong.

The improvements architecturally that Core2Duo brings are more L2 cache (4mb vs 2mb) and there are more pipelines and decode stages within the CPU, making it more efficient.

In terms of clock speeds, in notebooks, Core Duo ranges from 1.2ghz to 2.33ghz. C2D ranges from 1.06ghz to 2.4ghz. Most people will end up with the same speed processor (2ghz is typical), but clock for clock, the C2D can do more work.

Here is the real kicker. The C2D is designed to run on an FSB of anything from 533mhz ro 800mhz. 800mhz is the optimum speed. The CD only runs on 667mhz. However, all Macs only have C2D's running on 667mhz as well as their CD's, meaning they're essentially crippled.

Finally, the RAM each chip can address is the same. The C2D is a better CPU, but to get the most out of it, you need the 800mhz FSB, which I expect Apple will introduce next year.

I have no idea where you get your statements.
1. C2D is 64 bit by design. According to Intel, it features "Intel® Extended Memory 64 Technology."
2. The specification of C2D (mobile) indicates that the FSB is 667 MHz. Apple didn't do anything about that. The desktop version of C2D does have a higher FSB (1066 MHz) as a matter of fact.
3. As for the clock speed, the mobile version of C2D ranges from 1.66 - 2.33, and that of CD is 1.06 - 2.33.
And finally, C2D addresses more RAM than CD.

1. C2D is 64 bit by design. According to Intel, it features "Intel&#174; Extended Memory 64 Technology." This is something Intel put into the chip to enable support for 64-bit applications and address more than 4gb of RAM - since no notebook can even have more than 4gb of RAM, this feature is pretty useless. In fact EM64T was available in the later Pentium 4 models. I have to be honest, I didn't realise that CD didn't have EM64T and I was unaware that this difference existed between the two chips. It might explain the 60 million transistor difference.

2. The specification of C2D (mobile) indicates that the FSB is 667 MHz. Apple didn't do anything about that. The desktop version of C2D does have a higher FSB (1066 MHz) as a matter of fact. You're correct, but the point is that for the C2D to make the most of its additional pipelines and Cache, it needs more bandwidth and really needs a faster FSB to be efficient. Such a motherboard will shortly be available for notebooks.

3. As for the clock speed, the mobile version of C2D ranges from 1.66 - 2.33, and that of CD is 1.06 - 2.33. You're right, but being a C2D doesn't automatically mean the mhz is higher.

The bottom line, and this is only my opinion, is that the C2D is severely crippled in a MacBook or MBP because

- The 64-bit memory addressing will never get used, as this only benefits systems with more than 4GB of RAM (in fact application that need to address more than 4GB of RAM, meaning a system with 8 or 16GB at least)

- The FSB severely bottlenecks the system, because the chip isn't getting the memory bandwidth it wants to run effectively

- No 64-bit operating system exists for Apple. Leopard supports 64-bit, but again this is largely wasted on 4GB notebooks with 677mhz FSB speeds.

In the land of the blind, the one-eyed man is stoned to death.
- Joan D. Vinge

1. C2D is 64 bit by design. According to Intel, it features "Intel® Extended Memory 64 Technology." This is something Intel put into the chip to enable support for 64-bit applications and address more than 4gb of RAM - since no notebook can even have more than 4gb of RAM, this feature is pretty useless. In fact EM64T was available in the later Pentium 4 models. I have to be honest, I didn't realise that CD didn't have EM64T and I was unaware that this difference existed between the two chips. It might explain the 60 million transistor difference.

2. The specification of C2D (mobile) indicates that the FSB is 667 MHz. Apple didn't do anything about that. The desktop version of C2D does have a higher FSB (1066 MHz) as a matter of fact. You're correct, but the point is that for the C2D to make the most of its additional pipelines and Cache, it needs more bandwidth and really needs a faster FSB to be efficient. Such a motherboard will shortly be available for notebooks.

3. As for the clock speed, the mobile version of C2D ranges from 1.66 - 2.33, and that of CD is 1.06 - 2.33. You're right, but being a C2D doesn't automatically mean the mhz is higher.

The bottom line, and this is only my opinion, is that the C2D is severely crippled in a MacBook or MBP because

- The 64-bit memory addressing will never get used, as this only benefits systems with more than 4GB of RAM (in fact application that need to address more than 4GB of RAM, meaning a system with 8 or 16GB at least)

- The FSB severely bottlenecks the system, because the chip isn't getting the memory bandwidth it wants to run effectively

- No 64-bit operating system exists for Apple. Leopard supports 64-bit, but again this is largely wasted on 4GB notebooks with 677mhz FSB speeds.

Thanks for the input. Anyway, a few ideas:

- I don't quite understand why you say that the FSB bottlenecks the system. The RAM is 667MHz; the motherboard fully supports this bandwidth as well. Even there will be a motherboard that provides better bandwith, the reality is that the mobile version of the chips supports UP TO 667Mhz and won't go any further.
- I agree that 64bit is serves its purpose on Mac Pro and XServe, at this point...
- Tiger is not a fully 64-bit operating system. But its unix-layer is fully 64-bit. As Apple claims, "Mac OS X Tiger delivers the power of 64-bit computing to your Mac. Build and run a new generation of 64-bit applications that address massive amounts of memory, without compromising the performance of your existing 32-bit applications."

1. C2D is 64 bit by design. According to Intel, it features "Intel® Extended Memory 64 Technology." This is something Intel put into the chip to enable support for 64-bit applications and address more than 4gb of RAM - since no notebook can even have more than 4gb of RAM, this feature is pretty useless. In fact EM64T was available in the later Pentium 4 models. I have to be honest, I didn't realise that CD didn't have EM64T and I was unaware that this difference existed between the two chips. It might explain the 60 million transistor difference.

2. The specification of C2D (mobile) indicates that the FSB is 667 MHz. Apple didn't do anything about that. The desktop version of C2D does have a higher FSB (1066 MHz) as a matter of fact. You're correct, but the point is that for the C2D to make the most of its additional pipelines and Cache, it needs more bandwidth and really needs a faster FSB to be efficient. Such a motherboard will shortly be available for notebooks.

3. As for the clock speed, the mobile version of C2D ranges from 1.66 - 2.33, and that of CD is 1.06 - 2.33. You're right, but being a C2D doesn't automatically mean the mhz is higher.

The bottom line, and this is only my opinion, is that the C2D is severely crippled in a MacBook or MBP because

- The 64-bit memory addressing will never get used, as this only benefits systems with more than 4GB of RAM (in fact application that need to address more than 4GB of RAM, meaning a system with 8 or 16GB at least)

- The FSB severely bottlenecks the system, because the chip isn't getting the memory bandwidth it wants to run effectively

- No 64-bit operating system exists for Apple. Leopard supports 64-bit, but again this is largely wasted on 4GB notebooks with 677mhz FSB speeds.

Hey there,
I think I may have posted the other comment about C2D being 64bit capable.
I really want to understand your point here about the C2D's 64bit capability as the 64bit capability will be very important in my field in a few months. Is your point that the C2D does have the capability but it cannot be harnessed? Is your comment about the 4 Gig ram ceiling referring to physical limitations of two slots with max capacity of 2 Gigs each? If so, do you think it we may be seeing larger capacity ram sticks in the next 6-12 months? Sorry for all the questions but like I said, I really want to understand this as I have frankly never heard of the issue before.
-d

There is more to 64 bit technology than just accessing more than 4GBs of memory. Internally the chip is capable of working on 64 bits and can also transfer twice as many bits between RAM the and the processor in generally the same amount of time. Yes, there is more to it than that, such as bandwidth issues.

I recently decided that 64 bit technology doesn't mean much for me right now. Until Leopard is out and the software houses have at least recompiled for 64 bits, there isn't going to be a great gain there unless Apple does othe things, like adding the larger cache to the new Macbook Pros. Some of the lower level Unix stuff is already 64 bit, but I can't guess what programs take advantage of it.

That is the decision I made. I went with an older refurb Macbook Pro for $900 less than the new model I would have bought. If I made a living with my Macs, I likely would have got the C2D model because tests have shown it can be much faster for some things. Do you really need that extra horse power?